The things that kill smartphone batteries today are age and power cycles. It doesn’t matter if you charge from 0% to 100% in one go or from 90% to 100% ten times. Both add up to one power cycle.

To keep your battery fresh for as long as possible, always keep the phone connected to a charger. No battery cycles. It will get worse after a few years anyway.

> It doesn’t matter if you charge from 0% to 100% in one go or from 90% to 100% ten times.

This isn't really true, as far as I know. If you avoid fully charging or deeply discharging a lithium-ion battery, the wear per unit of energy extracted is smaller.

There are some statistics quoted here (https://batteryuniversity.com/learn/article/how_to_prolong_l...) showing that if you, say, halve the amount of energy you retrieve from a battery in each cycle, the battery lasts for more than twice as many cycles.

This paper arrives at a similar conclusion (see figure 4): https://www.researchgate.net/publication/318292540_Analysis_...

Thanks for the links!

Also, I want to add that what I wrote above is only regarding smartphones. I don’t know how much stress/extra heat etc that EV batteries are subject to, but I imagine they drain/charge at more intense rates relatively.

The principle applies for smartphone batteries too. Full discharges will degrade your battery significantly faster.

The sole reason I rooted my pixel 2 was to install a simple app which disables charging when I reach 80%. I get all the wins of not killing the battery by constantly saturating it, together with being able to leave it plugged in whenever I am at at my desk.

I so wish manufacturers would offer this option, for those primarily deskbound who do not relish ungluing their battery after a year

I think it is a built in (but configurable) option on newer Sony models.

Edit: they call it Qnovo Adaptive Charging and they get another minus from me [0] for making it impossible to select text on tye page by long-pressing it.

[0]: they got a huge minus from me back when they added "sponsored links" to my flagship Z3 or what it was.

Is it this one? https://f-droid.org/packages/com.slash.batterychargelimit/

Thanks for making me aware that such a thing exists.

Age, cycles and heat. Inductive charging loops are going to generate a ton of waste heat, and worse yet a good chunk of that is going to be coming from the coil inside the phone.

Yeah, but a battery gets hot when charging fast. Keeping it connected at 100%, the phone stays cool in my experience. And charging often makes the window where it generates heat from charging smaller

The act of charging the battery does itself generate some heat, as does the charging circuitry within the phone. This will happen with either method of charging. Wireless inductive charging will also generate significantly larger amounts of waste heat.

Fundamentally, wireless charging is less efficient. Theoretically you could be putting 16w of heat into the phone but only getting 8w of charging.

I dunno. All the EV manufacturers still recommend not charging to 100% daily.

EV batteries cost $5000+ to replace and are expected to last 7-10 years, maybe more if you push it. And they are a huge pain to recharge in the middle of the day if you suddenly need to. How many years do you plan to keep your phone for? Who cares if the battery only has 70% of original capacity after 3 years and on some days you need to find 20minutess in the middle of the day to leave it plugged in to recharge?

Thanks. Updated my post to say smartphones - I have no idea about what EV batteries are exposed to.